1. Field of the Invention:
The present invention relates to a control apparatus for an automobile air-conditioner driven by an engine and including a fast idling device for increasing the idling engine speed by a predetermined value when the air-conditioner is started.
2. Description of the Prior Art:
It is widely known that a motor vehicle having an air-conditioner driven by an engine of the vehicle is equipped with a fast idling device for increasing the idling engine speed to an extent corresponding to an increase in load offered to the engine by a compressor of the air-conditioner.
In view of a demand for power saving, for example, the compressors used in recent years generally comprise a variable displacement compressor. Owing to its peculiar features in construction and control performance, the variable displacement compressor is controlled in such a manner that the displacement is gradually increased after the compressor is started. Even in an air-conditioner having such variable displacement compressor, the aforesaid fast idling device is incorporated.
The fast idling device is activated when an air-conditioner start switch is turned on, whereupon the idling engine speed (e.g. 700 r.p.m.) is unconditionally increased by about 200 r.p.m. so as to accommodate the load on the compressor.
As described above, since the displacement of the variable displacement compressor is so controlled as to increase gradually after the start of the compressor, the engine load does not increase steeply in immediate response to the actuation of the air-conditioner start switch. Rather, the engine load increases gradually with an increase in displacement of the compressor.
As at the initial stage of operation of the compressor the load on the compressor is not so high, the unconditional activation of the fast idling device at this stage necessarily causes an undue rise in engine speed which results in a wasteful consumption of fuel. Further, in case of the motor vehicle equipped with an automatic transmission, there is a danger of abrupt starting due to such undue rise of engine speed.